The present invention relates to automatic transmission systems and, more particularly to an improved pressure regulator valve for Chrysler A518, 46RA, 46RE, A500, 40RH, 42RE, and 42RH transmission (hereinafter xe2x80x9cChrylster transmissionsxe2x80x9d).
Automatic transmission systems of the prior art have a hydraulic circuit subsystem which includes at least a hydraulic pump, a valve body having fluid conducting passages or circuits, input and exhaust ports formed within the fluid circuits, and a plurality of spool valves so-called because of their resemblance to sewing thread type spools. Such valves are comprised of cylindrical pistons having control diameters or lands formed thereon, which alternately open and close the ports to regulate the flow and pressure of automatic transmission fluid (hereinafter xe2x80x9cATFxe2x80x9d) within the fluid circuits to actuate various components of the transmission. It will be understood that in describing hydraulic fluid circuits, ATF usually changes names when it passes through an orifice or control valve in a specific circuit.
Pumps in automatic transmission systems are generally positive displacement pumps driven by the engine of the vehicle wherein the transmission is installed. A positive displacement pump is one, which has the same output per revolution regardless of pump speed or pressure already developed in the system. Thus, it is necessary to regulate ATF pressure so it does not get too high and damage other components. A basic pressure regulator valve employs a piston and a spring that compresses at a specific pressure to allow some ATF to flow back to the pump reservoir or sump bypassing the hydraulic circuit and reducing pressure. By using a pressure regulator valve with a compression spring calibrated to a pressure lower than the pump""s output, a constant ATF pressure can be maintained in the system during operation.
When the engine of the vehicle is turned off, ATF contained within the torque converter during operation gradually drains back to the fluid sump. At initial engine start-up this can result in an insufficient fluid level in the torque converter to operate the vehicle. Further, the original equipment manufacture (hereinafter xe2x80x9cOEMxe2x80x9d) pressure regulator valve does not send sufficient line pressure from the pump output circuit into the torque converter charge circuit in the Park gear range or at idle speed to refill the torque converter to permit instant operation of the vehicle with engine start-up.
Thus, the present invention has been developed to resolve this problem and other shortcomings of the prior art.
Accordingly, the present invention is a Lube Regulated Pressure Regulator Valve including an internal check valve that opens in the Park gear range and at low engine speeds to pass line pressure to the torque converter in response to a substantially lower hydraulic fluid pressure than is required to open the pressure regulator valve in its factory specified operating range. As engine speed increases and sufficient line pressure is built up within the torque converter charge circuit, the internal check valve is again closed and the pressure regulator valve opens as it would normally to feed line pressure to the torque converter directly. When the engine is shut off, the internal check valve is biased to a closed position preventing ATF from draining back through the valve to the fluid sump eliminating the aforementioned converter drain back problem.
Other features and technical advantages of the present invention will become apparent from a study of the following description and the accompanying drawings.